Stabilization of Sr-rich ultrathin epitaxial films of La2-xSrxCuO4

Highlights: • Ultrathin epitaxial films of La_2-xSr_xCuO₄ (x = 0–1) were grown by oxide MBE. • High Sr compositions have not been thoroughly investigated in the literature. • Smooth crystalline films are achieved for all x-values investigated. • Electrical transport and c-axis as a function of x are consistent with bulk. • Quality ultrathin films can be created across a wide range of Sr content. - Abstract: Varying the level of Sr in La_2-xSr_xCuO₄ produces a wide array of electrical properties, spanning metallic, semiconducting, insulating, and superconducting. While the system has been extensively studied, ultrathin films with high Sr content have not been reported. Using oxide molecular beam epitaxy, ultrathin La_2-xSr_xCuO₄ films (0 x x = 0 to x = 1.0 causes an initial increase and subsequent decrease in the c-axis lattice parameter and the surface roughness as a function of doping. The films exhibit analogous electrical properties to their bulk and thicker film counterparts. The ability to create ultrathin La_2-xSr_xCuO₄ films at high Sr levels shows promise for inducing unexpected electric properties through dopant modulation effects, such as cation ordering, digital superlattices, and atomically precise interfaces.